What humidity and temperature do cannabis clones need?
Fresh cannabis clones need 75-80°F (24-27°C) air temperature and 65-75% relative humidity to root successfully. Once established with visible roots, both metrics drop toward standard vegetative ranges — 72-78°F and 50-60% RH. Most clone failures stem from environmental conditions outside these windows: too cold and rooting stalls, too dry and the clone transpires faster than its roots can replace, too hot and disease pressure spikes.
Shop HLVD-Tested Clones →The rooting window: 75-80°F and 65-75% RH
During the first 7-14 days after a cutting is taken, the clone has no root system to draw water from soil. It survives entirely on moisture absorbed through its leaves. High ambient humidity (65-75%) reduces the rate at which the clone loses water to the air, while warm air temperature (75-80°F) accelerates root cell division. A heat mat under the rooting tray that brings the medium temperature into the 75-78°F range often makes the difference between rooting in 7 days versus 14. Domes or humidity tents over the cutting tray maintain RH; spritzing the dome interior with pH-adjusted water 1-2 times daily keeps the environment stable.
Easing off after rooting
Once white roots are visible, the clone can hydrate through its root system and no longer needs the high-humidity environment. Crack the dome to let humidity drop gradually over 2-3 days, then remove it entirely. Air temperature can also drop slightly toward the standard veg range of 72-78°F. Keeping a fully rooted clone in a high-humidity environment past this stage actually invites fungal disease — particularly powdery mildew and gray mold, both of which thrive at 70%+ RH on cannabis foliage.
Light intensity during rooting
Clones don't need much light during the rooting phase — and too much light is actually harmful. Target 100-200 PPFD (the equivalent of a 18-24 watt T5 fluorescent or a low-intensity LED at 18-24 inches). Strong direct light forces the clone to transpire harder than its underdeveloped (or nonexistent) root system can replace, leading to wilting and stalled rooting. Once established and transplanted, light intensity can ramp up to standard vegetative levels (300-500 PPFD).
Common environment mistakes
The single most common mistake is letting humidity drop overnight when grow lights are off and the room cools. Even if daytime humidity is in range, a single overnight drop into the 30-40% range can kill cuttings. Use a small humidifier on a timer if your grow space dries out at night. Other common issues: temperature swings of more than 8-10°F between lights-on and lights-off, propagation domes left fully closed for too long (causing condensation that drowns cuttings), and direct airflow from oscillating fans hitting the rooting tray (which dries cuttings out faster than humidity can compensate).
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